1. Field of the Invention
The invention relates to an arrangement for reproducing a digital signal from a track on a magnetic record carder, the arrangement including
a magnetic read head having a magneto resistive (MR) element, and wherein, viewed in the direction of transport of the track relative to the head, the magnetic head has a first side (front) and a second side (back), one of the sides having a magnetic shielding for the MR element which is larger than the magnetic shielding on the other side, PA1 an equalizer filter means, having an input coupled to an output of the magnetic read head, and an output, the equalizer filter means being adapted to supply an output signal at its output which has been substantially equalized as regards magnitude and group delay as a function of frequency, the equalizer filter means including finite impulse response (FIR) filter means, and PA1 transport means for moving the track in a certain direction past the magnetic read head.
2. Description of the Related Art
Thin film heads of the MRH type as described in the foregoing have been disclosed in the Journal `Electrotechnology`, April 1988, pages 61 to 64. When used in an arrangement for reproducing a digital signal from a track on a magnetic record carrier, an equalizer filter means is needed so as to compensate for the non-flat frequency characteristic of the reproducing system. The frequency characteristic of a system is expressed as a magnitude response and a phase response of the system as a function of frequency. The group delay of the system has a relation to the phase response of the system in that the group delay is proportional to the first derivative with respect to frequency of the phase response, or D(f).div..delta..PHI.(f)/.delta.f, where D is the group delay of the system as a function of frequency and .PHI. is the phase response of the system as a function of frequency.
It is known to use a FIR filter in the equalizer filter means. FIR filters are also called transversal filters, and are well known in the art of digital filter technology.
Prior art reproducing arrangements have the disadvantage that the equalizer filter means becomes very complex in that a large number of coefficients are needed in the FIR filter means in order to sufficiently equalize the signal read from the track. Such filter means realized in the form of an integrated circuit results in a large surface area of the substrate of the IC being occupied. Attempts to decrease the complexity of the equalizer filter means have led to a deterioration after equalization of the signal read from the tape.